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Re: [PATCH] Don't add useless reverse_op vta equivalences (PR debug/52001)


On Thu, Jan 26, 2012 at 10:03 PM, Jakub Jelinek <jakub@redhat.com> wrote:
> Hi!
>
> When a VALUE contains already some constant location, it will be always
> preferable to expressing it by some other expression - const (or some
> similar reverse operation), so we just should point at adding the
> reverse_op.
>
> This fixes the testcase from the PR on mips64-linux, bootstrapped/regtested
> on x86_64-linux and i686-linux, ok for trunk?

Ok.

Thanks,
Richard.

> 2012-01-26 ?Jakub Jelinek ?<jakub@redhat.com>
>
> ? ? ? ?PR debug/52001
> ? ? ? ?* var-tracking.c (reverse_op): Don't add any reverse operation
> ? ? ? ?if V already has any constant locations.
>
> --- gcc/var-tracking.c.jj ? ? ? 2012-01-23 18:23:45.000000000 +0100
> +++ gcc/var-tracking.c ?2012-01-26 16:37:20.110049563 +0100
> @@ -5298,6 +5298,7 @@ reverse_op (rtx val, const_rtx expr, rtx
> ?{
> ? rtx src, arg, ret;
> ? cselib_val *v;
> + ?struct elt_loc_list *l;
> ? enum rtx_code code;
>
> ? if (GET_CODE (expr) != SET)
> @@ -5333,6 +5334,14 @@ reverse_op (rtx val, const_rtx expr, rtx
> ? if (!v || !cselib_preserved_value_p (v))
> ? ? return;
>
> + ?/* Adding a reverse op isn't useful if V already has an always valid
> + ? ? location. ?Ignore ENTRY_VALUE, while it is always constant, we should
> + ? ? prefer non-ENTRY_VALUE locations whenever possible. ?*/
> + ?for (l = v->locs; l; l = l->next)
> + ? ?if (CONSTANT_P (l->loc)
> + ? ? ? && (GET_CODE (l->loc) != CONST || !references_value_p (l->loc, 0)))
> + ? ? ?return;
> +
> ? switch (GET_CODE (src))
> ? ? {
> ? ? case NOT:
>
> ? ? ? ?Jakub


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